Method of improving macrostructure of titanium-base alloy products

ABSTRACT

A METHOD OF IMPROVING THE MACROSTRUCTURE OF TITANIUMBASE ALLOY PRODUCTS BY ADDING TO THE ALLOY ABOUT 0.03 TO 0.40 PERCENT YTTRIUM, WHICH MAY BE EITHER THE METAL ITSELF OR A COMPOUND THEREOF. ADDITION OF YTRIUM ACHIEVES A FINE GRAIN STRUCTURE AND AVOIDS SPANGLED SURFACES ON MACROETCHED SECTIONS OF THE PRODUCT, BUT USUALLY LOWERS BOTH THE YIELD STRENGTH AND ULTIMATE TENSILE STRENGTH OF THE PRODUCT. INVENTION COMPENSATES FOR THIS LATTER EFFECT BY ADJUSTING THE CONTENT OF STRENGTHENING AGENTS, PREFERABLY OXYGEN OR NITROGEN.

Ju ly 25, 1972 H. B. BOMBERGER, JR., EFAL METHOD OF IMPROVING MACROSTRUGTURE 0F TITANIUM-BASE ALLOY PRODUCTS 'Ffiled May 5. 1970 H W 'n mmm FIG. 2. mv 'umz IN VE N T01 HOWARD B. BOMBERGER, J

STANLEY R. SEAGLE By Walla.

A Harvey United States Patent ()fiice $222122 3,679,403 METHOD OF-llVIPROVING-MACROSTRUCTURE F TITANIUM-BASE ALLOY PRODUCTS Howard B. Bomberger, Jr., Canfield, and Stanley R. Seagle, Warren, Ohio, assignors to RMI Company, 'Niles,0hio" 1 Continuation-impart of application Ser. No. 749,269,

Aug. 1, 1968. This application May 5, 1970, Ser. No.'34,674

- Int. Cl. C22c 15/0 US. Cl. 75-1755 9 Claims ABSTRACT OF THE DISCLOSURE This application is a continuation-in-part of our earlier co-pending application, Ser. No. 749,269, filed Aug. 1, 1968, now abandoned.

This invention relates to a method of improving the" macrostructure of titanium-base alloys and to the resulting product.

Coarse grain structures or a spangled surface condition 'cent by weight. The remainder of the alloy may consist of any combination of the usual alloying elements for titanium; including aluminum, tin, vanadium, zirconium, chromium, molybdenum, iron, oxygen, nitrogen and others. Our method is applicable to alloys which con- .tain alpha and/or beta phases. Surprisingly it is not applicable to unalloyed titanium nor to alloys which contain less than about 3 percent by weight ofalloying elements.

According to our method, we incorporate in the alloy about 0.03 to 0.40 percent by weight yttrium. Since yttrium is costly, we prefer to add it in the minimum quantity to achieve the desired improvement in macrostructure of the alloy. Additions of yttrium to produce a content in excess of our upper limit tend to make alloys more difficult to work, even though they may achieve the desired improvement in macrostructure. We may add yttrium to the alloy either in the form of the metal itself or a compound, such as the oxide Y O provided the other elements in the compound have no adverse eifect on the final alloy or are within allowable limits. We prefer to use a compound for reasons that compounds are less costly, and other elements of the compound may supply a strengthening agent, as hereinafter described. In adding yttrium to an alloy, we may follow the usual technique interfere with sonic inspectionof titanium-base alloy 7 a 30-inch diameter ingot of a titanium-base alloy to a Y 20-inch diameter billet is not suflicient forthis purpose, and the billet usuallyis coarse-grained. Even though a product may be worked sufiiciently to achieve a fine grain structure, macroetched sections of the-product may have spangled surfaces which similarly hamper sonic inspection.

An object of the present inventionis to provide a method of improving the macrostructure of titaniumb ase alloy products through yttrium additions without adversely affecting other properties.

.A. more specific object is to provide a method of improving the macrostructure of titanium base alloy products in which we add yttrium to the alloy, but compensate for the adverse eifect on tensile properties by increasing the content of strengthening agents, preferably oxygen and/or nitrogen. i

A further object is to provide an improved titaniumbase alloy product which results from practicing our method.

Our method is applicable to alloys which contain a minimum of about 70 percent by weight titanium. Most alloys for which our method is useful have a titanium content no greater than about 95' percent by weight, and our preferred range is about 70 to 95 percent titanium. Nevertheless our method may be useful for some alloys;

which have a titanium content" as" high" as aEoutQTprof combining yttrium metal or a yttrium compound with sponge titanium and the other alloying elements in a consumable electrode, and melting the electrode with an electric arc to form an ingot. Yttrium has little solubility in titanium, but tends to form a fine refractoryv oxide precipitate with a melting point above 4300 R, which is substantially higher than the melting point of titanium.

Table 1, which follows, demonstrates the benefits we have obtained in controlling the grain size of various titaniur n ba se alloys by adding yttrium.

TABLE 1 Grain size 1 As cast Beta arm.

Composition, wt. percent: Ti-6Al4V Large 2 90Ti-6Al-4V .OlY do 1 90Ti6Al-4V 03Y Medium..- 2 90Ti-6Al4V .05Y--- Small- 3 90Ti-6Al-4V.+ .10Y do '4 90Ti6Al-4V 15Y. .-d0-. 5 90Ii6Al-4V+ 10YaOa .--do 4 90Ti-6Al-4V .20Y203 -do '5 92.5Ti-5Al-2.5Sn Large l 92 5Ti-5A.l2.5Sn 05Y Small 2 73Tr13V-11Gr3Al Large- .1 73Ti-l3V-11Cr-3Al .05 SmalL- 3 Tl Large 1 100'1i .lY do.. 1 IOUTi .lYzOs 1 92.5Tl5Al2.5Sl1-.1Y2O3 SmalL- 4 73Ti-l3V-1l Cr-3Al.l YrO 0-- 3 97Ti-1.5Al-1V Large- 97Ti1.5Al1V-.1Y Medium 95Ti-3Al-2V 95Ti3Al-2V.1Y 86Ti-5Al-9S1L. a 86Ti5A.l-9Sn-AY 5 Grain sizes-ASTMnumbers and L, M and S for large, medium and 2 Sheet (0.040-inch) annealed 50 F. above the beta transi temperatures.

In the drawing: I FIG. 1 is a photograph of a macroet ch ed surface pf a titanium-base alloy product'ih which there is no yttrium;

and

ingot to a billet about 4 inches in diameter, and was reheated as required between forging operations. The work strate that increasingamounts of yttrium lowers the thus performed on the alloy was suificient to achieve 5* strength more more."

TABLE 3.TENSILE PROPERTIES OF COMliIERCIAL TI-6A1-4V 0.025" BAR WITH YTTRIUM ADDITIONS I a UTS, YS, El, RA

j Heat number Composition Kai. Ks.i. ,percent percent 29055 'Ii-fi.4Al-4.3V-0.18Fe-0.170 155 j 135 8.5 18.0 29059-.- Ti-6.4Al-4.3V-0.18Fe-0.17 +0.05Y I 150 129 12.5 29.;1 29060 Ti-ti.4Al-4.3V-0.18Fe-0.17 0+0.10Y "148 127 12 7 32. 2 29061. Ti-5.4Al4.3V-0.18Fe-0.17 0+0.20Y 145 I 125 33.3

desirable fine grain size regardless of whether 'the alloy contained yttrium. The alloy shown in FIG. 1 (Heat N0. X29297-1) in which yttrium is absent has an objection ably spangled surface. The alloy shown in FIG. 2 (Heat No.X29299-1) hasno spangled surface. Table 2, which follows, demonstrates'th" elfect of'yttrium additions in increasing the sensitivity of sonictestin'g for flaws in billets of 6-4 alloy. A No. 5 Hole Test is a sonic test adusted to locate flaws %2 inch; or more in diameter internally of a test specimen. A"No. .3 Hole Tes is a similar test adjusted to locate flaws 05 inch of morein diametenThe results of the test are observed on anoscilloscope. The Noise is the percent of the oscillo scope scale reading which is induced by back -sc'atter within the test specimen where there is no measurable ITY OF Ti-6Al-4V BILLET 1 Also in accordan with ourinvention, we adjust the content of one or morepf the strengthening' agents cantainedjn the alloy'to compensate for the adverseeifect content "of about 0.17% by weight. When we add yttrium to this alloy,we find both the yield point and the ultimate tensile strength may drop by about 4 to 10K s.i.' unless we compensate by adiusting the content of one 'or more strengthening agents. We ;may restore the tensilestrength of the alloy by raising the oxygen content by about 0.01' to 0.06%. As anotherexample, the titanium-base alloy whichnominally'contains Gpercent aluminum, 6 percent vanadium, 2 percent tin, and the balance substantially 'rnnnn a-nrrnc'r or Y'r'rmtm ADDITION'ON moams'me some 'rns'rmo SENSITIV f H w Number 5 hole test Number 3 hole test 2. 7 Number 5 hole test Number 3 hole test2 I Percent Bm t {u Background, percent 7. Background, percent e s Heat number Y0 Yttrium inches 1 Ma noise Ave. noise Mar. noise Ave. noise 0 35, 11 75 17 0.07 .do- 15 5.5 50 11 0.15 do 20 1: 5.5 55 11 0 4, round- X 0. .07 .-..do '10 12029-1 (Figure 2)- 0.19 0.15 do None 1 Background noise due to grain structure interiereswith the'sensitivity of sonic testing torsrnaller defects. I Tested ior defect levels oi 5/32 and 3/32inch hole diameter. Noise level is percent oi detect scale range. 8 Background noise interferes when sonic testing at a smaller defect size. 7

----However, -we have further discovered that adding yttriumto titanium-base alloys usually has an undesirable $49; 93%;. t l wer the .1n e-s gt ofthe product. In our aforemenioned earlier application, we gave test results which might lead onejto the opposite conclusion, but we obtained these results with tests on sheet material which had been worked and annealed at relatively low temperatures. Hence the results were not representative of products .of heavier cross section, such as bar stock. Thelatter products must be worked at higher temperatures that is, above or near the beta transus. If the alloy is not worked at low temperatures, our more recent tests demonstrate that additionof yttrium tends to lower both the yield strength and ultimate tensile strengthof many vtitanium-base alloyproducts by as much as 10K s.i. mi

Table 3, which"follows, shows the resultsof tensile ee wrm a se i of o-62i n hb te qrmed. owe-4,". alloy. In these .tests wemaintained the oxygen content at v0.17% and increased the yttrium content of the different bars from nil to 0.20%. The results demon- 0 TABLEIZL-T-TENBILE PROPERTIES titanuim (6- 6-2 alloy) icommonly' has an oxygen con tent of about 0.16% by weight. When we add'yttriu'm, we may compensatefor the'loss in tensile strength byr'aising' the oxygen content 'againby about" 0.01 to 0.06%.---W e may achieve similar compensation by adjusting the' 'oii: tent of 1 other strengthening agents, "notably nitrogen, which is a more potent strengtheningagent.thanoxygen; Both the "'6- 4" and the 6-64 alloys commonly havea nitrogen content of about 0.01% by weight. When we Table 4, which follows, shows the results of tensile" testswe performed on series'of 0.625 inch bars formed of 6-4 alloy and 6-6 2-alloy'.' In these tests wetested control-specimens of each alloy, specimens in which we added yttrium without adjusting the oxygen content, and other'specimeiis in which we added yttrium and adjusted the 'oygen contentin accordance with the present invention..

or COMMERCIAL Tl 6A1-4VAND Team-eves AND YTTRIUM OXIDEADDITIONS n 0625 BAR WITH YTTBIUM' Aim oxygen,

Heat percent in- Measured. 1 p

r V oxygen UTS Y8 El RA number Composition Base YiO: percent Heat treatment K sin K. s.i'. percent 'percent' mm. '1i-e.4A.l-4.3V-0.l8Fe .170 .204 1,840 F.-1 hr.-AC 157 131 8 2 15 5 20000. '1i-6.4.Al-4.3V-0.18Fe+0.1Y .160 1,840 F.-1 hr.-AC-- 143 127 12.7 32:0 2028. -6.4Al-4.3V-0.18Fe+0 lY .196 1,840 F.-1 bra-AC" 125 14.0 i 33.1 m. Pi-5 4Al-4.3V-0.18Fe+0 llYsOs .186 1,840 F.-1 hr.-.AO 151 121 11. 7 32. 0 m4. Ti-6 LAl-4 3V-0.18Fe+0 11Y|O| 208 1,840 F.-1 hr.-A 155 132 e 11.5 29 7 M41- Ti-5 6Al-5 6V-2.1Sn-0 7Cu-0 7Fe 184 1,800 F.-1 hr.-F 144 127 13. 5 I 7 m. Ti-5.6Al-6.6V-2.1Sn-0 7Cu-0.7Fe+.09Y: .182 1,800 F.-1 hr.-F 140 i V 125 15.0 27 2 20244. Ti-5.6A1-5.6V-2.1Sn-0.7Cu-0.7Fe+.09Y. 183 .190 1,800 F.-1 hr.-FC 120 15;0 25:9 M47. 'Ii- 6.6Al-5.6V-2.1Bn-0.7Cu-0.7Fe+0.11YsOs 137 .023 .'175 1,800 F.-1 hr.-FO. 141 127 15.5 27.3 mm.-- Ti-5.0A1-5.6V-2.18n-0.7Cu-0.7Fe+0.11YgOs 160 023 1,800 F.-1 hr.-F 141 1% I 14.5 28.1

5 Table 5, which follows, shows the efiect of yttrium oxide additions on 0.625 inch bars of a number of other titanium-base alloys.

pensation is obtained by raising the oxygen content by about 0.01 to 0.06 percent.

6. A method as defined in claim 1 in which the yttrium TABLE 5.EFFECT OF YTTRIUM OXIDE ADDITIONS TO SEVERAL TITANIUM ALLOYS Aim oxygen,

percent in- Measured Heat oxygen, UT Y El, RA, number Composition Base YaOa percent Heat treatment K s.1 K s.i. percent percent 29249.- Ti-3A1-2.5V 140 156 1,800 F.-1 hr.-AC- 109 89 17. 7 41. 29248-- Ti-8Al-2.5V-0.11YO; 140 023 143 1,800 F.-1 hr.-AC 107 89 18. 8 46. 7 29252.- Ti-4Al-4V 150 173 1,800 F.-1 I'm-AC" 124 103 15. 7 39. 9 29253 Tl-iM-4V-0JIYIO: 150 0. 23 163 1,800 F.-1 hr.-AC 125 106 16. 0 44. 9 29261-- Ti-6Al-8V 150 149 1,750 F.-1 hr.-AO 157 131 10. 5 21. 8 29260.- Ti-6Al-8V-0.11YO 150 .023 .174 1,750 F.-1 hr.-AC 153 128 12. 5 29.6 29258-. Ti-7 4M0 .150 150 1,950 F.-1 hr.-FC.. 134 118 12.0 19. 7 29257.. Ti'7Al-4Mo'0 llYgOa 150 023 158 1,950 F.-1 hr.-FC 138 123 16. 3 30. 2 29256 Ti-5Al-2.5S110.2Fe .150 .154 1,920 F.-1 hr.-A 131 119 14.0 23. 2 29254 Ti-5Al-2.5Sn0.2Fe-0.11Y:O .150 023 .179 1,920 F.-1 hL-AC" 134 122 14. 0 31. 5 29250 Ti-SAl-lMo-IV .150 .166 1.955 F.-1 hr.-AC 151 134 10. 7 18. 2 29251 Ti-8Al-1Mo-1V0.11Ya0a 150 023 169 1,955 F.-1 hr.-AC 144 124 13. 0 30. 5

From the foregoing description it is seen that our invention affords a simple, reliable method first of improving the macrostructure of a wide variety of titanium-base alloy products, and second overcoming any adverse effects on the product.

We claim:

1. A method of improving the macrostructure of titanium-base alloy products which contain about 70 to 97 percent by weight titanium, the improvement being in reduction of the grain size and in the elimination of spangled surfaces on macro-etched sections, said method comprising adding to the alloy about 0.03 to 0.40 percent by weight yttrium, and compensating for the loss of tensile properties which would otherwise result from the yttrium addition by raising the content of at least one of the strengthening agents of the group consisting of oxygen and nitrogen above the normal level present in the alloy in the absence of yttrium by amounts of about 0.01 to 0.06 percent by weight of the alloy in the case of oxygen and 0.01 to 0.03 percent by weight of the alloy in the case of nitrogen.

2. A method as defined in claim '1 in which the oxygen content is raised by about 0.01 to 0.06 percent.

3. A method as defined in claim 1 in which the nitrogen content is raised by about 0.01 to 0. 03 percent.

4. A method as defined in claim 1 in which yttrium is in the form of its oxide when added, and the oxygen present in said oxide supplies the increased content of strengthening agent.

5. A method as defined in claim 1 in which the alloy nominally contains 6 percent by weight aluminum, 6 percent by weight vanadium, 2 percent by weight tin and the balance substantially titanium and has a normal oxygen content of about 0.16 percent by weight and in which comis in the form of the metal when added, and the increased content of strengthening agent is added separately.

7. A method as defined in claim 1 in which the alloy nominally contains 6 percent by weight aluminum, 4 percent by weight vanadium and the balance substantially titanium and has a normal oxygen content of about 0.17 percent by weight and in which compensation is obtained by raising the oxygen content by about 0.01 to 0.06 percent.

8. A method as defined in claim 7 in which yttrium is in the form of its oxide when added, and the oxygen present in said oxide supplies the increased content of oxygen.

9. A product obtained by the method of claim '1.

References Cited UNITED STATES PATENTS 3,028,234- 4/1962 Alexander et al. -175.5 X 3,070,468 12/1962 Grant 14820.3 3,113,991 12/1963 Kleber 75-175.5 X 3,141,235 7/ 1964 Lenz 75-- 176 X 3,205,099 9/1965 Vordahl 1484 3,310,398 3/ 1967 Kneip 75-175.5 X 3,360,366 12/1967 Bonis 75178 OTHER REFERENCES Nuclear Science Abstracts, vol. 13, No. 23, December lgazngbook of Chemistry and Physics, 46th ed., 1965-66, p.

Journal of Nonferrous Metals, No. 1, 1959 (Russian), Sauitskiy et al., pp. 2, 5, 9 and 10.

CHARLES N. LOVELL, Primary Examiner 

